United States Patent 3786479

A display system that uses a digital storage and processor having stored therein a plurality of sources of binary coded information representative of a plurality of display messages and patterns. A graphic generator converts coded information into analog stroke or painted display information. This stroke information and/or asynchronous display information from other sources is converted into television raster information which is then cyclically stored on a magnetic disk, together with displays from other synchronous noncoded and coded sources as well as live television. A plurality of remote stations can select any display information which is converted as necessary to raster video information. These frames may be recorded on one or more tracks of the magnetic disk. This information is then applied to the television monitor at the station. The operator at the station can then control the processing of the binary coded information and request other display material while viewing the monitor and in addition, can correlate portions of images on the CRT display with the originating digitally controlled stroke information. Furthermore, raster information of several selected tracks as well as synchronized video from other sources can be compared and/or mixed.

Brown, Caroll J. (San Jose, CA)
Chesarek, Donald J. (Los Gatos, CA)
Fisk, Dale E. (San Jose, CA)
Ma, Joseph T. (Los Gatos, CA)
Martin, Harold F. (Chappaqua, NY)
Reynolds, Zack D. (San Jose, CA)
Application Number:
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Filing Date:
Primary Class:
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International Classes:
G06F3/033; G09G1/04; G09G5/393; (IPC1-7): G06F3/14
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US Patent References:

Primary Examiner:
Trafton, David L.
Attorney, Agent or Firm:
Broidy, Thomas A.
Parent Case Data:


The present invention is a continuation of my copending application Ser. No. 782,154 now abandoned, filed Dec. 9, 1968, and assigned to the same assignee as this application.
We claim

1. Display system comprising:

2. Display system as set forth in claim 1 wherein said portion of said display is a rectangle determined by a pointer and preselected coded boundary signals in said digital processing means.

3. Display apparatus as set forth in claim 1 wherein said memory means includes a plurality of discrete binary information representative of a plurality of visual displays,

4. A display system for digital and analog information, said system comprising

5. The display system of claim 4 wherein at least one source of beam directing and intensification or video information is coupled to the input of the scan converter means; and



A display system wherein the displays originate from a digital processor storage unit and other sources.


In computer display systems, binary-coded information is stored which represents a particular message or pattern to be displayed on a cathode ray tube. This binary information is decoded into a form suitable to be applied to the display device such as an analog signal to deflect an electron beam in a stroke type movement of an electron beam. In order to regenerate the display, the predetermined information is cyclically accessed and repeatedly applied to the display. A plurality of displays are frequently employed which have access by some remote means to the processor.

The prior art display signals normally only emanate from one source, that is, a computer or photographic slides or a tape recorder, etc., since normally it is not feasible to accommodate other sources.


It is therefore an object of this invention to provide a new and improved display system having a central processing unit which can originate and modify displayed information.

A further object of the invention is the provision of a new display system for selectively applying image forming signals to a display device wherein the digital display information in the computer or files can be processed and changed without affecting the visual image.

A still further object of the invention is to provide a new and improved display system that has a high degree of flexibility, and can accommodate various sources of displayable information.

Still another object of this invention is the provision of a new and improved display system that can utilize various sources of visual displays with a minimum of complexity at the display station(s).

Still a further object of the invention is to provide a display system that can identify a point or area on the display with a minimum of interruption and/or computer processing time.

The above objects of the present invention are realized in one form thereof by employing a computer based system which contains a plurality of storage locations having binary information representative of a plurality of displayable frames of messages or patterns. This coded data is selectively converted to television raster information which is then buffered and regenerated in this noncoded form. This noncoded information is cyclically regenerated to thereby provide a visually continuous display on a monitor. By cyclically regenerating the noncoded information, the binary coded information in the computer representing this display can be processed, modified, compared, etc., without affecting the visual display at the remote station.

As a further feature of the invention, a means is provided at the remote station to generate XY information of a particular point on the display. This information is compared with signals corresponding to spatial coordinates which are provided at the output of a graphic generator prior to scan conversion into raster video form. In so doing, process time of the computer processor is saved, and display signal regeneration is not interrupted.


FIG. 1 contains a schematic diagram partially in block form of a display system embodying the invention,

FIG. 2 illustrates a graphic generator together witha scan converter suitable for use in the embodiment in FIG. 1,

FIG. 3 illustrates an electron beam deflection path, and

FIG. 4 illustrates a block diagram of a system suitable as a coordinate compare.


The above objects of the present invention are accomplished by a system connected to a digital storage and processor 10 that has a plurality of storage locations containing binary coded information, representing a plurality of separate images. Control means 20 can be actuated by keyboard 100 or other suitable means to effect movement of the data for an image to a graphic generator 30 which transduces the binary coded information into X, Y and Z signals which are capable of deflecting an electron beam to thereby provide a stroke type display or pattern. This X, Y, Z information is selectively applied to an electron beam type scan converter 40 or 50 which converts the X, Y, Z display information into television type full frame formatted raster video information which can be a time sequence of analog or digital signals. The output of the scan converter is applied to a track selector 60 which then switches this video information to a magnetic disk storage 70 having a plurality of endless tracks thereon. Tracks of the magnetic storage unit 70 are read out through a distribution network 80 to provide raster displays by a plurality of remote television monitors such as 90. Also, at the remote station and positioned adjacent to the television monitor 90 is a coordinate identification means 110 which identifies XY locations of selected portions of the displayed image provided by monitor 90. Other sources of images such as from films or real scenes come from a scanner or television camera 150, a video file or tape recorder 160, or a television camera 170.

When the signals are provided in noncoded video form (such as analog) from the storage disk 70, they are regenerated and produce a continuous visual display on the monitor such as 90. The computer-derived display source is also simultaneously present in coded form in the digital storage and processor 10. Thus, while the image is being regenerated and viewed in noncoded form, the image in coded form can be scanned and utilized or processed in the digital processor 10. The coded image can be analyzed, compared, modified, etc., while the displayed noncoded image is being viewed without interruption. In addition, without interrupting this viewing, the image in noncoded video form can also be compared and/or coordinated with other images on the disk.

The magnetic disk storage 70 includes a clock track having clock pulses thereon which develop horizontal and vertical raster sync. Since the binary coded information is not being regenerated to provide a regenerative display and since the readout of the scan converter is synchronized with the sync signals from the storage disk, the scan converters 40 and 50 can then be used, without interrupting the display, to convert exterior asynchronous display information to synchronous display information. Synchronous exterior video sources can also be applied to the monitors or records on the disk in response to the synchronizing pulses developed from the clock pulses on the disk. The clock track can have conventional vertical and horizontal television sync pulses applied thereto for two video fields so that when using a conventional monitor synchronization for 525 lines is provided. The read out of the scan converters 40 and 50 is synchronized with the clock pulses or sync pulses on the clock track.


The digital storage and processor 10 includes a plurality of frame storage locations 11, 12 and 13, each of which contains binary coded information representing a message and/or patterns for an individual image shown as number 1, number 2 and number N, respectively. As illustrated, the binary coded information is a series of binary words with each word representing a letter or numeral by way of an alphanumeric code. In these codes, such as used with the IBM 2250 display, normally the words consist of six to eight binary bits. When this information is applied to a conventional graphic generator 30, the output thereof will be analog X and Y signals (horizontal and vertical electron beam deflection signals) as well as a Z signal (analog or digital beam gating signal).

In addition, the storage locations 11, 12 and 13 could contain images other than alphanumeric. In such a case, binary coded words may represent end points of lines. These end points would then be converted to X and Y (horizontal and vertical) analog deflection signals that would deflect the electron beams from one end point to another as well as Z or beam gating signals to enable proper intensification of the beam. Other suitable generators that convert binary coded information (of images) to displays are shown in U.S. Pat. Nos. 3,334,304 and 3,205,488. Also see January 1961 Proceedings of IRE, pp. 185-195.

The operator at station S can effect, by way of keyboard 100, commands from the subsystem control 20 to selectively transmit the binary information for one image from location 11, 12, etc. to a graphic generator 30.

The graphic generator 30 converts the binary-coded information to analog X and Y deflection and Z gating or intensification information that is suitable to deflect an electron beam in a stroke type form such as is common in graphic displays and, as illustrated in FIG. 3, (which provides an electron beam path of the number seven by moving the beam from A to B). This stroke type deflection is converted to television raster type information by applying it to either a scan converter 40 or a scan converter 50.

FIG. 2, for purposes of clarity, sets forth in more detail a conventional type graphic generator such as is employed to convert binary coded display information into alphanumeric stroke information. THe graphic generator 30, so illustrated, continuously has digital X position information which is applied to a coarse D to A converter 31 and Y position information which applies to a coarse D to A converter 32. The output of converter 31 is applied to an amplifier or yoke driver 33 and the output of converter 32 is applied to an amplifier or yoke driver 34. Conventionally, the coarse X information provides a signal representing the distance from the sides of the display at which a character starts to be written and the Y information indicates how far from the bottom or the top of the display (which line) the start of the character writing begins. Fine information is provided to a character generator 35 which converts this binary coded information into fine X and Y information analog and Z information which could be digital or analog. Thus, if the binary fine information from the processor indicates an A to be written, the character generator provides the analog deflection signal for the X and Y deflection yokes, necessary to write an A at or from the point determined by the X and Y coarse information. The X fine analog signal is amplified by amplifier 37 and combined with the coarse analog signal at point C. The Y fine analog deflection signal is combined with the coarse analog deflection signal at point D. Character generator 35 furthermore generates an intensity signal which passes through the intensity amplifier 36 to vary the current of the electron beam by varying the bias on a grid 41. If the display is to be digital this signal will merely turn the electron beam on and off as is known conventionally.

The typical scan converters 40 and 50 which are illustrated herein may be a type of electron beam storage tube such as a television camera or vidicon tube described in more detail in co-pending application, Ser. No. 775,861, filed Nov. 14, 1968 in the name of John W. Brookman, Johm B. Murphy, Zack D. Reynolds and entitled "Photo Erasable Scan Converter" and assigned to the same assignee as the present invention. This co-pending application describes a television camera tube in which an electron beam is applied to the target in a stroke fashion and then the target is read out in raster form by the electron beam. Any suitable scan converter, such as a storage tube, could be employed for the function defined herein. For the purposes of illustration, the storage tube 40 includes a cathode 47, a grid 41 which could gate on or off the electron beam or vary the intensity of the beam by the output of the Z intensity amplifier 36. The coarse and fine X deflection signal combined at point C is applied to the X deflection yoke 42. The fine and coarse Y deflection signal combined at point D is applied to the Y deflection yoke 43. During write, switches 46a and 46b are up.

Thus, the binary coded information defining one image is converted by generator 30 to electron beam analog stroke information to provide an image on target 44. During readout, switches 46a and 46b are down and the yokes 42 and 43 are deflected in the conventional raster mode by deflection circuits 46 so that the target 44 develops at the output 45 a typical raster or television type signal. The output of the scan converter 40 or 50 is selectively applied to a cyclic storage means such as a magnetic disk 70 by way of a channel selector 60.

The track selector 60 selectively applies the raster information from either scan converter 40 or 50 to one of the plurality of magnetic tracks TR1 through TRN by way of magnetic heads 71 through 71N. The magnetic disk 72 is rotated at 1,800 rpm so that each rotation of the disk takes the time normally used or elapsed for the recording or playing back of one video frame (two interlaced video fields). The disk can be rotated at 3,600 rpm so that the time for one rotation of the disk is equal to the time required for one video field. In such a case, two tracks would have to be utilized to provide one video frame by alternately switching between these tracks.

A separate track TRC is employed on the disk 72 with this track containing vertical and horizontal synchronizing pulses required for one video frame. In a conventional television system, this would require 525 horizontal sync pulses and two vertical sync pulses. The signal on the track TRC is either the required number of the sync pulses, horizontal and vertical (for one frame) or conventionally a multiple of pulses are recorded with the frequency divided down by a sync generator 74 to provide the required number of vertical and horizontal sync pulses.

When the actual horizontal and vertical sync pulses are recorded, the sync generator 74 is not needed but rather the output of head 73 is connected directly to the circuits 46 of scan converters 40 and 50 so as to provide proper synchronization of the horizontal and vertical raster circuits 46 shown in FIG. 2. In addition, the head 73 would also be directly connected to the distribution network 80 where the sync signals will be added to the video information from any of the tracks TR1 through TRN. Alternatively, two tracks may be employed for the synchronization function of TRC, one with horizontal sync pulses and one with vertical sync pulses. Sync pulses are made available for other sources 150, 160 and 170 to provide a synchronous input directly into the track selector 60. Alternatively, the clock track TRC could contain a multiple number of clock pulses which, when divided down, will produce 525 horizontal sync pulses and two vertical sync pulses. This division occurs in the sync generator 74 and operates in the same fashion as is done for developing sync pulses for a conventional television camera. An example would be that the clock track contained 6,300 pulses with this output being divided by 12 to produce 525 horizontal pulses and divided by 3,150 to produce two vertical sync pulses. The magnetic head 73 is employed to record these pulses and thereafter reads these pulses out (when appropriate) to a sync generator 74 which divides the frequency of the pulses down to provide both the horizontal and vertical synchronization pulses.

Recording a different number of pulses on TRC and dividing by different numbers in the sync generator 74 will allow television displays having other than 525 lines to be generated. This could be down to generate displays compatible with 873 line closed-circuit television monitors, for example.

It will be understood that the video information applied to the tracks TR1 through TRN could be applied on a carrier such as an FM carrier and then recorded on disk 72. Such a suitable selector 60 and FM recording is illustrated in co-pending application Ser. No. 682,432 filed Nov. 13, 1967 in the name of J. L. Adkisson and A. B. Manildi. On readout, an FM demodulator is used to drive the video signal.

The heads 71 through 71N are always connected to a distribution network. In so doing, the video information is applied through the network 80 to a monitor such as 90, even during writing or recording so as to provide a non-interrupted display drive. A display selection can be accomplished by way of the keyboard terminal 100 which is connected to the subsystem control 20 to thereby command the readout of one of the storage locations 11 through 13 to the graphic generator 30, or to select an alternative input such as 150, 160 or 170.

Since the magnetic disk storage 70 regenerates to produce a continuous display on the monitors such as 90, other auxiliary displays can more easily be provided in the system such as photographic file 151 which can be picked up by a scanner or TV camera 150. Furthermore, a TV camera 170 can provide live information for displays. Both 150 and 170 can be connected to a video file or tape recorder 160 or alternately to one of the scan converters 40 or 50 in asynchronous mode; in a synchronous mode, they may be connected directly to channel selector 60, thence to disk storage 70, and directly to distribution 80 for displaying continuously scanned information. When transducers 150, 160 and 170 are connected to the scan converters 40 or 50 in asynchronous mode the horizontal and vertical sync pulses from generator 74 are employed to provide synchronous readout therefrom.

Thus, it is seen that in a conventional type display, the binary coded information in the computer is normally directly converted into either stroke or video raster information and applied to a monitor. As such, the only video displays possible from any storage or regenerating means must come from the computer. In the present invention, however, it is seen that the binary coded information is converted first into a stroke image and then by using the scan converter, it is converted into raster information. As stated above, these scan converters are read out in synchronism with the sync pulses on the cyclic storage means such as disk 72. Thus, it is seen that by utilizing this double transformation of the image, it is possible and easily adaptable to include in the system virtually any asynchronous display source by applying it to the input of the scan converter. Furthermore, synchronous raster information can be applied directly to the channel selectors and this image information can come also from virtually any source of raster information. It will be understood, of course, that this noncoded raster information can be analog in form similar to a conventional television signal and also can be digital display information where only on and off information on the electron beam provides the display. Furthermore, it will be understood that this noncoded information could be applied to a carrier such as by frequency modulating the carrier in a conventional manner. In such a case, demodulators would be present in the distribution system 80.

It will be noted that a single record and read head is employed for each track so that during recording the information will continue to be supplied to the monitor connected to that particular channel.

As stated above, vertical and horizontal sync pulses are applied either to a single track or two tracks on the disk 72. Normally, coded signals for a single binary coded display message or pattern are applied to the graphic generator and the resulting XYZ signals are applied to a scan converter, so that a single frame will be read out from the scan converter through the channel selector 60 onto the disk 72 when actuated by the vertical and horizontal sync pulses from track TRC. Asynchronous sources are normally applied to a scan converter for conversion to a synchronous output and to accommodate differing resolutions, field sizes and types of scan. They may then be applied through track selector 60 for direct recording on the disk. In this case, either the vertical sync pulses or a single home pulse on disk 72 can be applied to gate these inputs so that signals corresponding to only a single frame will be recorded on the tracks 71 through 71N.

An additional feature is that by regenerating the raster information on disk 72 in the form described above, relatively inexpensive television monitors can be employed, resulting in a relatively large cost saving when a number of output channels or stations are in the system.

The XY locator 110 provides two digital output signals which represent the XY position of a pointer 113 on a tablet 114. Various conventional means can be employed to produce the desired XY signals. Such an example is illustrated in U.S. Pat. No. 3,399,401 in which a tablet is employed which does not overlay the display but rather is below or to one side of the display. In such a case, coordinates on the tablet 114 correspond to coordinates on the display. The details of such a system will not be shown, but for purposes of illustration, a converter 111 is shown to develop digital YO coordinate signals from the pointer 113 and converter 112 is shown to illustrate developing digital XO coordinate signals from the signals from the pointer 113 and the tablet 114. Any suitable system which would so produce binary or digital X or Y coordinate signals in response to positioning of pointer 113 can be employed.

In the system shown in U.S. Pat. No. 3,399,401, the tablet is not transparent and thence cannot overlay the display. If it is desired to have a system wherein the identifying area overlays the display, such systems as illustrated in U.S. Pat. No. 2,338,949; 3,527,835 and 2,241,544 can be employed. These systems in general utilize two pairs of plates in the X and Y direction across which an AC signal is employed. A pointer is employed on the display, and the resulting AC output signals from the system which varies as the pointer is moved, can be rectified and converted to an analog signal which subsequently can be converted to digital signals to provide XY digital coordinate signals. This XY digital information from locator 110 is selectively applied to a coordinate compare 140. The other input to the compare 140 selectively is the XY generator 30. Thus, the operator can regenerate the information in the graphic generator 30, and compare it with the point selected by pointer 113 in the coordinate compare 140. When coincidences of the X and Y signals occur simultaneously, an output is provided which, by way of proper timing or clocking, identifies this point within the subsystem control 20.

More specifically, when the difference or distance, between the XY position signals from graphic generator 30 and the corresponding X O YO signals from pointer 113 are within a selected range, coincidence is recognized. A means is provided either in the unit 10 or unit 20 to indicate the range of coincidence. This comparison can either be done in an analog form or digital form. As a particular example, if the comparison, in fact, is done digitally in the compare unit 140, the XO Y0 signals from pointer 113 (if not in digital form originally) would be passed through analog to digital converters, the output being the contents of one register containing the XO position and one register containing the YO position. Likewise, the X and Y information from generator 30 would be passed through analog to digital converters to provide at the output thereof an X position and a Y position. THe contents of these converters, of course, would be dynamic and change as the output of generator 30 changes. When the magnitude of the difference between X and XO and between Y and YO is less than a value established by coded limits from the digital storage and processor 10, a coincidence true condition is established. When coincidence is detected, either the position registers from graphic generator 30 could be stopped or the binary coded display information to the graphic generator could be interpreted so as to locate the position of the particular code or step within the stream of data and orders which initiated the X, Y position placement. Additionally, the X, Y coordinate position at coincidence could be obtained from XY registers of 30.

The multiplex means 130 is employed to selectively apply the signals from pencils such as 110 at a plurality of display stations, to the coordinate compare circuit 140.

FIGS. 3 and 4 illustrate a method of comparing the coordinates identified by the pointer 113 and the output of the graphic generator 30. In FIGS. 3 and 4, the computer is adjusted so as to determine if a stroke from a graphic generator goes through the window W shown in dotted lines in FIG. 3. To this end the signals from the pointer 113 and tablet 114 are passed through converters 111 and 112 to provide binary signals representing XO and YO, the position of pointer 113. Alternatively, pens, pointers, or teaching devices with direct digital output may be used. The digital processor provides a selected window by providing arithmetic unit 141 with, as shown, -ΔX+ΔX, -ΔY and +ΔY. The -ΔX is added to the XO to provide an XL coordinate output as shown in FIG. 3. The +ΔX is added to the XO to provide a binary XR output. The -ΔY is added to the YO to provide a YL binary coordinate output. The +ΔY is added to the YO to provide a YU output. These coordinates are representative of the boundaries of the window W as shown in FIG. 3, as illustrated therein in dotted lines. The X deflection applied to deflection coils 42, during compare, is applied to an A to D converter 144 which provides a binary indication of the horizontal coordinate of the electron beam in converter 40. XL, XR and the output of A to D converter 144 are applied to an arithmetic unit 142. This unit has a one output when X is larger than XL and smaller than XR. The output of this unit is then applied to AND gate 146.

Point D is connected to A to D converter 145 so that Y deflection current applied to coils 43 of converter 40 provides a binary indication of the vertical deflection of the electron beam in converter 40. The YL, YU outputs of unit 141 are applied to an arithmetic unit 143. Likewise, the output of A to D converter 145 shown as Y is applied to unit 143. When Y is larger than YL but smaller than YU, there will be one output from 143.

A variation of the preferred method is to convert XL, XR, YL, and YU to analog voltages by using digital to analog converters after the arithmetic function 141, while eliminating analog to digital converters 144 and 145. In this case, the compare functions 142 and 143 are accomplished with analog threshold circuits. As used in a binary mode so that the beam is either off or on, the output of Z amplifier 36 is also applied to AND gate 146. Thus, if units 142 and 143 have a one output, the deflection currents have directed the beam within the window W. When the beam is on so that the Z input to 146 is also a one, the intensified beam is passing through the window W. It will be understood that this window W can be altered in many ways to provide various functions. If shown as a square, it allows a predetermined tolerance to identify a position of the beam. It could, for example, however, by a horizontal line, by making Δ+Y and +ΔY both zero. Thus, the pointer 113 and the beam could be moved up and down to effect a bountary indicator or a height comparator.

When used as a window to provide tolerance in selecting a beam trace, the output of the AND gate 146, as stated above, will be a one when the beam passes through the window W. This output could, for example, stop the reading out of the display information from one of the locations 11 through 13 to thereby identify within the computer exactly the program step which corresponds to where the pointer 113 is pointed. Thusly, this identifies in the storage location within the computer, the area of interest without requiring any work done by or programming of the computer. Alternatively, a counter in the subsystem control could be employed to count the output words by bytes of the selected display location 11 through 13. When an output occurs from AnD gate 46, this output would stop this counter which would identify the byte or bit within the storage locations 11 through 13 that the pointer 113 has identified. It will be understood that the multiplex means 130 has not been shown in FIG. 4 for purposes of clarity. This, however, would be located between the locator 110 or other digital coordinate indication signal lines and the arithmetic unit 141 solely for switching purposes.

In addition to the other features, two channels can be connected from the output of the distributon network 80 to compare these channels in a raster compare unit 120. The compare unit 120 will compare the signals of the two channels in analog or digital form and by conventional logic will provide an output signal defining the presence and/or magnitude of any difference between the signals.

The subsystem control 20 can be actuated by the station keyboard 100 or processor so as to actuate and control various positions of the system illustrated in FIG. 1. For example, this control system is connected to graphic generator 30 so as to command the generator to produce alphanumeric symbols as well as to produce displays from data in locations 11, 12 or 13 by reading out from processor 10 into generator 30 and then to a scan converter 40 or 50. Furthermore, the control 20 is connected to scanner 150 and photographic file 151 to select a predetermined image on the film 151. Likewise, the subsystem control is connected to tape recorder 160, and television camera 170 to thereby select images from either of these sources. The image selected from 150, 160, 170 can be, as stated above, synchronous or asynchronous. Other portions of the system controlled by the subsystem control 20 via commands of the keyboard 100 are the switches S1 and S2 to select scan converter 40 and 50, the channel selector 60 to determine the channel selection, the coordinate compare 140 to effect coordinate compare, and raster compare 120. In providing coordinate compare, it will be understood that normally the pointer 113 will be manually positioned at the desired point and then the selected coded display from locations 11, 12, and 13 will be fed into the graphic generator 30.


When the operator at the remote station S desires a particular display, he actuates ths subsystem control 20 by way of a keyboard 100 which thereby selects an output from one of the storage locations 11, 12 or 13 to be applied to the graphic generator 30. These storage locations contain binary coded information representing a display. This graphic generator generates XY stroke type electron beam deflection signals and Z intensity or beam gating signals from the binary coded information signals which are then applied to the scan converter 40 or 50. While this stroke information is applied to the scan converter, e.g., 40, as shown in FIG. 2, switches 46a and 46b are up (and closed) applying deflection signals from the graphic generator 30 to the pairs of deflection coils 42 and 43. The amplifier 36 is connected to the control grid 41 of the scan converter, which in the preferred embodiment is a conventional vidicon tube 40 operating in darkness. The Z information from 36 being applied to grid 41, gates on and off the electron beam from cathode 47. It will be understood that the Z information could be applied so as to gate the cathode 47 directly without being applied to the control grid 41. During readout, the electron beam emanating from the cathode 47 of the scan converter vidicon tube, sweeps the target 44 in the conventional raster mode (as done with a conventional television pickup). This provides a conventional television raster signal at the output terminal 45. During readout, switches 46a and 46b are down (and closed) so that the horizontal and vertical deflection circuits 46 apply conventional raster deflection signals to the pairs of deflection coils 42 (horizontal deflection) and coils 43 (vertical deflection).

It will be noted that, by utilizing the scan converters in this system, various display sources 150, 160 and 170 can be fed into the scan converter although they are asynchronous and may have scans differing from the system output standard. The readout of the converter then delays, synchronizes, and insures the correct scanning sequence of the video signals, since the circuit 46 is driven or synchronized by vertical or horizontal sync signals from generator 74. Alternately, where feasible, the units 150, 160 and 170 can have their readout synchronously driven directly by the sync signals from 74. In such a case, the outputs thereof are applied directly to the distribution means or through track selector 60 to the disk storage 70.

Commands from keyboard 100 to control 20 may directly or indirectly via control programming select the scan converter (40 or 50) to be utilized. In addition, commands from keyboard 100 to control 20 condition selector 60 to selectively apply the output of scan converter 40 (or 50) to one of the tracks TR1 to TRN on disk 72 providing a display for monitor 90. Thus, it is seen that the graphic generator 30 and the scan converter 40 and 50 are a means to convert binary coded information from the processor 10 into video raster information. This conversion could be achieved by other translation techniques. Such a recording and switching (of unit 60) is set forth in detail in the above co-pending application Ser. No. 682,432.

After so recording, this frame of display information continues to be regenerated on disk 72 and displayed on the CRT of monitor 90. When the operator desired to process corresponding binary coded information in CPU 10, he does so by way of keyboard 100 through control 20 or by pen feedback using coordinate compare. This information can thereby be modified processed within processor 10, etc., without disturbing the displayed image as originally provided by this coded information from 11, 12 or 13. This is in contrast to other systems that recirculate the binary coded information in unit 10 or in an associated buffer memory to produce the display.

If the operator desires to locate a point on the display, he employs the pointer 113 that develops XO YO coordinate signals of a point on the display. This signal is compared with signals being generated from the graphic generator 30 in the coordinate comparator 140. This enables identification of intermediate points within displayed symbols or line segments not represented by binary coded information in the processor, without complicated processing within unit 10. As set forth above, it is generally desirable to identify an area through which a portion of a displayed construction passes, such as shown in FIG. 3, and identified as W. The processor 10 provides digital signals representing the dimensions of this area in -ΔX, +ΔX, -ΔY and +ΔY. The pointer 113 provides digital XO and Y0 information which specifies the position of area W and which are added to the ΔX and ΔY information to define the sides of the window W identified in FIG. 3 as XL, XR, YU and YL. When a trace of the beam on target 44 passes through such a window, there is an output from AND gate 146 which then can effect an indication of the position of the pen relative to the displayable information, without the use of translation in the processor 10. THis is made possible by comparing the information from pointer 113 with the stroke information in the generator 30. As stated above, the window W could be made various sizes of a rectangle or even a line. Further, when identifying a line element of the display, this window provides a programmable tolerance limit.

While in accordance with the Patent Statutes, we have described what at present is considered to be the preferred embodiment of our invention, it will be obvious to those skilled in the art that various changes or modifications may be made therein without departing from the present invention.